How to Apply Polyurethane to Vertical Surfaces? Photo Guide

To apply polyurethane to vertical surfaces, prepare the surface by cleaning and sanding it, use foam brushes to apply the polyurethane sparingly in thin, even coats, and ensure proper drying. Oil-based polyurethane is the best choice for vertical surfaces as it dries slower and provides better penetration.

Applying polyurethane to vertical surfaces can be challenging, requiring specific techniques and tools to achieve an even and bubble-free finish.

This article will provide tips and tricks from a test we did to apply polyurethane to vertical surfaces, helping you achieve a beautiful and durable coat.

Applying Polyurethane to Vertical Surfaces: Step-by-Step

Supplies needed to apply polyurethane to a vertical surface
Supplies needed to apply polyurethane to a vertical surface

Polyurethane coating is an excellent choice for protecting wooden surfaces, but applying it evenly on vertical surfaces can be challenging.

By following the instructions below, you can achieve an even coating on vertical surfaces without bubbles, sags, or runs.

Supplies Needed
Foam brushes
Sandpaper (120-grit)
Cleaning supplies (e.g., cloth, detergent)
Supplies needed for the project

Preparing for Application

To achieve a high-quality finish when applying polyurethane, prepare the surface before application.

Proper surface preparation can mean the difference between an even and durable finish or a shoddy and uneven one.

Take the time to clean the surface thoroughly, removing any dirt, dust, or debris that may interfere with the polyurethane’s adhesion.

Cleaning the wood surface with a brush
Cleaning the wood surface with a brush

Additionally, sand the surface with fine-grit sandpaper to create a smooth and even surface that will promote proper adhesion and coverage of the polyurethane.

Using Foam Brushes

Using the right tool is crucial when applying polyurethane coating on vertical surfaces like doors, windows, and decor.

One of the best tools for this job is a foam brush. Foam brushes have a pointed tip and a flat front, making it easy to reach corners and tight spaces where bubbles may accumulate.

Applying polyurethane to wood surface using a foam brush
Applying polyurethane to a wood surface using a foam brush

Compared to bristle brushes, foam brushes are less likely to leave marks and are more comfortable for extended periods.

However, many find foam brushes unfit for polyurethane application due to their tendency to leave air bubbles.

Despite this, I swear by foam brushes for their effectiveness in applying polyurethane on vertical surfaces.

With the right technique and careful attention to detail, a foam brush can help achieve a smooth, even finish.

Applying Polyurethane Sparingly

One of the most common polyurethane mistakes is applying too much at once, leading to bubbles and uneven application.

To avoid this, apply the coating sparingly during the initial stages and gradually build up the layers as needed.

This provides better control over the coating applied and reduces the likelihood of bubbles forming.

Using the right type of polyurethane is also important for achieving the desired finish.

Oil-based polyurethane is a popular choice for vertical surfaces because it dries slower than water-based polyurethane, allowing more time to work with the coating.

When using a brush, such as a foam brush, dip it into the polyurethane and lightly tap on the edge of the can to remove any excess.

Dipping and taping the foam brush in polyurethane
Dipping and taping the foam brush in polyurethane

Applying the polyurethane in thin, even coats will prevent drips and bubbles from forming.

Sanding Between Coats

To achieve a professional-looking finish when applying polyurethane to vertical surfaces, lightly sand the surface between coats.

This is important when dealing with wooden surfaces, which tend to have a rough texture.

Sanding helps remove imperfections that may have settled on the surface during drying, such as dust particles and small bumps.

Sanding the initial coat of polyurethane
Sanding the initial coat of polyurethane

I recommend using 120-grit sandpaper to sand the surface lightly before applying the second coat of polyurethane.

This grit is coarse enough to remove any roughness on the surface while being fine enough not to leave any visible scratches.

Before sanding, ensure the surface is completely dry and free of debris. Use a clean tack cloth to wipe the surface to remove any dust or dirt.

Remember, sanding too much can cause the surface to become too smooth, and the polyurethane will have difficulty adhering to the surface.

Therefore, sanding lightly is the key to achieving a smooth, even finish without damaging the surface.

Apply the Final Coat

The final coat of polyurethane is crucial to achieving a perfect finish.

Evenly coating the surface prevents the formation of dry spots, which can be difficult to fix without leaving smears or globs of coating.

I recommend using a foam brush with a pointed tip to avoid this issue to reach tight spaces and apply the polyurethane coating smoothly.

You should move the brush slowly to avoid generating bubbles and carefully inspect the surface after each stroke.

If you find any bubbles, burst them immediately with a toothpick or a fine bristle brush.

Removing bubbles from PU after it dries
Removing bubbles from PU after it dries

The right technique and tools can help you achieve an even, smooth, and flawless poly finish on vertical surfaces, such as doors, windows, and decorative pieces.

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Frequently Asked Question

Can polyurethane be applied to a vertical surface?

Yes, polyurethane can be applied to a vertical surface. In fact, it is often used for vertical or contoured surfaces, along with round surfaces, due to its excellent adhesion and durability. Polyurethane can provide a protective coating and enhance the appearance of various vertical surfaces, such as walls, doors, and cabinets.

What is the best way to apply polyurethane to a large surface?

The best way to apply polyurethane to a large surface is by using a foam roller or a paint sprayer. These tools provide even coverage and minimize brush marks. It is also important to apply the polyurethane in thin, even coats and allow proper drying time between each coat.

Is it better to brush or roll polyurethane?

It is better to roll polyurethane on a large, flat surface for a smoother and more even finish. However, brushing can be effective for smaller areas and for adding detail. To avoid brush marks, using a high-quality brush and applying the polyurethane in thin, even coats with light pressure is important.